Hi Mike! Thank you for your question and welcome to HCM.
I know that this really worries you. It seems just like a benign cystic collection of blood based on your description. However, it is very difficult to precisely give you a diagnosis without actually seeing the bump, examining it, and running some tests. For the exact diagnosis, I suggest that you get it examined and treated by a dermatologist
In the meantime, clean the open wound and apply pressure on the bump using a clean, sterile bandage until the bleeding stops. Keep the wound covered, clean, and dry until you see the dermatologist.
I sincerely hope that I was able to answer your question and help you in this dilemma. If you have any further queries, please do not hesitate to ask me (http://doctor.healthcaremagic.com/doctors/dr-rene-gerard-cruz-galera-jr/66134).