Why am I having blood under the nails?

Hello everyone, I'm 23F and I recently started experiencing blood under both of my nails seemingly out of nowhere. Although I've noticed it appears more on the nails on my left hand. This started about 3 months ago, and I went to my GP and had a blood test done but it came back normal. It goes away every few days than comes back, no pain but quite unsettling to see it, and I'm not sure what's happening. In my medical history I have not been diagnosed with anything and I do not taken any medication. I've also tagged a photo of it.

https://imgur.com/a/cbE9CCP