I woke up with a bruise on my leg with a little red dot in the middle doesn't hurt or anything just wondering what it is?

Bite. This is possibly an insect bite and I would say nothing to worry about as long as it does not get worse or infected. Apply ice and it usually heals by itself.
Bite or pimple. Impossible to diagnose without a picture and more history. If the leg is red and warm and swollen around the red dot go see a doctor. It might be a staph infection or an infected bug bite.