Doesn't look like one to me, but it would be unusual for a plant to be showing sex this early, especially a female unless you're growing from clones. Just wait, if it's female some pistils will grow out the end.
Looks like the shape of a female preflower, but I can't see from the pic if it has two little hairs coming out of the end? Give it a few days to a week to be sure, but looks female probably...