How To Remove Painful Soft Bump On Thumb?

I HAVE A SOFT BUMP JUST UNDER THE SKIN ON MY THUMB BY THE KNUCLE. I DON'T FEEL IT UNTIL I WRITE OR BEND IT. THEN IT HURTS. IT IS NOTICIABLE TO LOOK AT IT. TO PUSH ON IT IS NOT PAINFUL ONLY TO BEND. I HAVE HAD THIS FOR A MONTH OR SO. WILL IT JUST GO AWAY. I HAVE HIGH, HIGH DEDUCTIABLE AND DON'T WANT TO SPEND MONEY IF IT WILL GO AWAY. THANKS