Went to urgent care two days ago. had my cyst drained a bit. he gave me bactrim (sulfamethoxazole and trimethoprim). now my cyst has developed a pus head. should i drain it or let it be?

See your doctor: I would not suggest you to do anything but you want to go back to your doctor to make sure there is no recurring abscess.

Best NOT: If the cyst was drained and you are on appropriate antibiotic it ought to gradually resolve. Applying heat frequently will help some. It may open and drain on it's own, but if needing drained again, it would be best performed by a professional. Just because a lesion is coming to a head, does not mean necessarily that it is ready to be opened. You might check back with the people who drained it.