This happens a lot to carpenters who use their penis as a hammer. Seriously, it would be odd for an old injury to periodically produce a blood blister. Are you sure that you are not re-injuring yourself? If it is, indeed, a recurring blister from an old injury, you'd need to go to a dermatologist and get the spot cauterized. That will keep it from recurring.
It doesnt periodically produce the blister its always there unless i pinch the skin causing the blister to dry up and come off. it will then just come back after some time if I do that. I have thought about cauterizing it actually would something like a wart removal kit do the job? I don't feel like having a doctor do this if I can take care of it my self..
Do yourself a favor, please go to the doctor and make sure of what you have and the correct way to take care of it.
I know what it is I clearly remember causing it with that electric razor..
Don't try it yourself. It's not a wart. A dermatologist has an electric cauterizing tool. It will take three seconds and sting just a bit. That should do it. If it's something else, the doc could identify it.