Do you have any pain now? I would definitely take the antibiotics first and see if that helps to resolve the issue. If he isn't able to find the end of the canal, it may be possible that he filled past the end of the root and into the jaw bone (which may explain why you had pain during the gutta percha step). Nothing to be worried about in most cases. You can always bring your concerns up with your endodontist and seek a second opinion as well.
What kind of complications can gutta percha being injected into the gum cause?
There is a circle of white filling (gutta percha) after the procedure on the x ray and he said "well thats how it filled out at the tip" ...this is scary.. and also do you believe this can cause caitations?
sorry meant to say "jaw bone" instead of "gum:"
If its into the jawbone and literally just in the bone, it should be no problem. If its the sealer/cement they used to seal the canal when they put in the gutta percha, your body will probably dissolve it in 6 months or longer. If the gutta percha is out but pushing something its not suppose to, such as your sinus or a large nerve tract, then it can create complications. You may want to ask your dentist to check your x-rays to see if it is but if it was, I'm pretty sure he would've informed you.