Sorry to disagree, but none of the gentlemen that I know that have used yogurt to relieve their problem quickly have never complained that it made their condition worse.
It is always important to seek medical advice and get a swab taken of the area to get the correct diagnosis and appropriate treatment.
Natural yogurt is ideal as a home remedy to help deal with urgent problems. Natural yogurt has antifungal properties and is also cooling to any inflamed areas of the skin.
I agree with the above except yogurt used to be the home treatment prior to the anti-fungal medications going over the counter (OTC). By applying a moist paste-like yogurt to the affected area will only make the situation worse. You will want to consult your doctor and pharmacist first on the treatment.
What you can do (probably with assistance) to keep the anal area dry prior to treatment is to clip the hairs in this area. Be careful not to cut yourself!
It is highly likely that you have a fungal infection.
Make an appointment to see your doctor so that a swab can be taken to find out if it is a fungal.
If it is a fungal infection, you will need an anti-fungal cream to apply to the washed and dried penis. The doctor may prescribe an anti-fungal cream and/or antifungal oral medication as well. You can buy these things without a prescription at the pharmacy. If you speak with the pharmacist he will be able to advise you which medication would be suitable for you.
Best though is to go to the doctor and get a swab taken or go to the GUM clinic.
Not only will you require an antifungal medication, presuming that this is a fungal problem, you will also need an emollient to apply to keep the area lubricated so that it does not dry. Dry skin can also cause itchiness and there are other skin problems like Lichen or dermatitis that can occur on different parts of the body.
In the meantime, do not use normal soaps to wash your genitals. Only use soaps with the same pH levels as our skin or get a good medicated emollient from the pharmacy (your doctor may prescribe one for you). Use this instead of soap. Wear cotton underwear and avoid manmade fabrics. Use latex free condoms in the event you may have an allergic reaction to the latex. Use non-biological washing detergents and fabric softeners that are suitable for people with allergies. Do not wear tight clothes.
As a home remedy, after you have gently washed and gently dried your genitals you can apply natural set yogurt to the penis and surround sore area. You can apply this for as long as is required and it will cause no side effects.
But do get checked out to get the correct diagnosis and the appropriate treatment.
Best wishes