blood blister

I was making beer the other night, and the top of the 7 gallon fermenter pinched the end of my index finger, immediately giving me a reasonably large sized blood blister, and hurting like a son of a bitch. Didn't break the surface, but immediately flushed red under the surface. Now, about four days later, it's exactly the same size, and a dark red.

My brother still has a mark from a blood blister he got when he was young, and he told me that when he gets one, he cuts it open and cleans it out, otherwise it will stay forever. I would prefer not to cut myself.

Does anyone know if this always happens, or does your body know how to cure itself of blood blisters? I just feel like my body should be smart enough to notice that there's dead blood under the surface of my skin and fix it. But I'd rather not have a scar for life.