Hello & Welcome to Just Answer,
May I ask you a few questions in order for me to understand your situation better thereby allowing me to help you better:
1) Can you move your finger/ make a fist with your affected hand?
2) Has an X-ray been taken?
3) What would be your age?
4) Any other medical conditions/ significant history?
Thanks. Shall be waiting for your reply.
Sorry for having gone away, and had left the message of being away so that some other expert should help you in my absence. I am really sorry that this reply has not been given so far and my sincere apologies for that.
Having gone through your descriptions, it seems that a bony injury is very likely and this needs to be confirmed/ excluded by a thorough clinical and an X-ray examination. It seems that we probably have a displaced fragment of bone which has made its presence as a small bony lump at the base of your index finger since the past two weeks following the bad bruise against a wall.
Having said that, you are right about seeing your doctor for it, as if indeed it is a displaced fragment of bone or maybe a dislocation perhaps of the metacarpo-phalyngeal joint (base of finger), it would need appropriate care and management. At times, with a bad bruise, a foreign body can also get embedded deeply to feel like a bony lump (if the foreign body is hard), but then there would also be an open wound of entry in that case. Please check in with your doctor and get yourself examined thoroughly so that a cause could be detected which would direct appropriate management.
I hope that this information helps. Best wishes. Please feel free to enquire if you have any remaining concerns/ doubts, as it shall be a privilege and a pleasure to try and help as much as I can.