I’m literally losing my mind.

I’m literally losing my mind. I recently got fungus on my toes, but I just noticed this on my thumb the other day. I scrubbed and I scrubbed with soap and it’s not coming off. It’s not a stain. Here’s a picture of my thumb and the rest of my fingers for nail color context. Is this the start of fungus on my thumb? UPDATE!!! - my nail is back to its normal color. It turned yellow because I had been peeling clementines with my hands and mainly this thumb for several days in a row