Hi Chris,
Welcome to the Pain Mangement Forum. I am sorry to hear about your painful joint.
RICE, Rest, Ice, Compression and Elevation is the cardinal treatment for an injury. However "rubbing" should not have injured your knuckle. It may be possible that the rubbing triggered an existing problem. But stranger things have happened.
If it continues to be bothersome or becomes worse by all means consult your PCP. Please let us know how you are doing.
Best of luck and Take Care,
~Tuck
Yeah you had better go and see a doctor,it could be any number of things.