If you know of anything they sell in the US and not in Israel I can probably send it to you. We send packages to our family there all the time.
It almost looks like maybe an acid burn. The flesh appears charred, but the fur not cinged. I would highly recommend a vet. The wound is highly susecptable to infection if not already set in. He must be in pain even if he's not letting on to it.
If, and only if a vet is not available to you, the wound needs to firstly be cleaned. This may be difficult as to how he will react. It is going to hurt. It needs to be flushed and any dirt/debris removed. Then it needs to be dry completely. A non-stick "skin" type covering needs to be applied. I don't know if you can buy these things in Israel like in USA. They are usually found in our drugstores in the bandage area and marked for use on burns. If antibiotics are not over the counter and you cannot get a prescription, you can order Penicillin on line at drsfosterandsmith dot com. They are in the fish medication area. Most vets rx amoxicillin. I would say he would be given 100mg 2x a day. My cat weighs about 5-6lbs and she is rx 65mg 2x a day.
Like I said though, if you can get him to a vet, that is the best way. The poor darling! If he can be kept indoors, it would be best. Whoever hurt him is likely to do it again.
Oh my gosh! That is so horrible, who knows what that poor cat has been through? It does look like animal cruelty or torture of some sort. I know you are hesitant to take him to the vet but if he is not taken to the vet, an infection will occur if it hasn't already and that will put him in more pain. Also, if the cat is being subjected to animal cruelty, he is likely to get injured some more, maybe even killed. If it were me, I'd take him in and care for him and get him treatment and never let him go out on the streets again by keeping him or at least taking him to an animal shelter of some sort where he'd be looked after. Keep us updated on him, that just breaks my heart.
I agree with Savas. You should take him to a vet. He doesn't look good. Even if he doesn't seem to be in pain he is in pain. I think that the wound, like savas said may have been caused by abuse. God knows what that poor animal has been through.
I could be wrong but it looks to me like a collar/rope injury...but the extremity suggests some sort of animal cruelty or torture.
You have to take him to a vet. Based on what I'm seeing the only question likely in whether they put him down is whether or not you're willing to pay/take care of the situation. This injury absolutely needs stitches and antibiotics. As long as you say it's been, it's not able to heal properly and most likely won't without some help. Eventually, it will infect and lead to any number of fatal results.
Sorry. As awful as it looks, in one sense it's not a fatal/ serious health issue if treated properly (keeping in mind I have no info about the cat's health otherwise or any additional damage beyond the surface skin injury). Alot depends on the state of the remaining skin, and sooner is better as tissue necrosis will make treating it harder.
Oh God! The wound looks really bad. I'm sure the cat will need antibiotics but I don't know if you can get it over the counter in Israel. To my knowledge, antibiotics is prescribed in USA but I'm not quite sure. I'm sure Savas has more answers. He can help you better as he has been working with cats for quite some time. Poor Kitty. Good luck.