During covid lockdown, I masturbated a lot but instead of the normal way of doing it I rubbed it in-between my body and bed. While doing this, I had my hand in-between by body and the bed. After doing this prior for the previous years and never having any issue, my left index finger knuckle started hurting a lot after I was done. For many days I didn't care but now at this time, it hurts some days and other days it feels off. I am going to the doctor in a month for my annual checkup and am going to mention it but I just wanted to ask here to see if anyone might have any idea what the issue could be.