I Have A Sore On My Glans Penis That Does

I have a sore on my glans penis that does not want to heal. I know for sure it is not an std, have been taking bactrim for protititus for a while. 59 years old. tried taking benadryl for a week. the sore starts to heal but then keeps opening back up. another spot on the glans looks like it could become a sore but has not so far any ideas to get this to heal.