I Have An Infection On The Left Thumb. It Accurs

I have an infection on the left thumb. It accurs under the nail itself and can spreed around the side of the nail. It is a yellow liquid. This happens and can go for several weeks and then can re apear. The infection can last a few weeks. I have had this for a couple of years. The pain hurts, it gets a little hard and painfull when preasure applied.
Thank you