My son had a pimple at the top of the crease of his buttocks that apparently popped and drained while he was in the shower. When he got out of the shower it was bleeding. Upon inspection, there is a small, open hole where the pimple and pus were previously. The blood was bright red, no further pus came out, and there was no foul odor. After thoroughly cleaning, I had him place a non-stick pad in the area so we could see what, if anything further drained, and to keep an eye on the wound. It is in an awkward place. What should I be looking for to warrant a trip to the physician for this type of wound?