You could just yank it out and not worry. Those are the first/cotyledon leaves of a seedling. It’s a bit difficult from that pix...if it was a tomato, or sunflower or gourd type....id be able to give you a good guess. Give it another week and take some more pix.
It looks like it might be a gourd/squash type...time will tell.
Good luck
Give it a chance to put out its true leaves.
A watched pot never boils, as they say.