I had a skin biopsy of my back which ended up being melanoma. I then needed a deep biopsy to make sure it had not spread, which it didn’t. Definitely get it done ASAP.
I foolishly did any olympic tri later that week. Swimming was painful (but bearable) from the tension on the surgical wound. I don’t think it effected by performance. In comparison, wounds from my bike crash (larger, but not nearly as deep) was worse regarding training/performance. Knowing what I know now, I shouldn’t have done the tri. I work in infectious disease and open wound with open water is not a good idea. Once the wound is closed, you’re fine to swim.