My orthodontist put a power chain between my 2 front teeth 2 days ago, it was a big gap. now there is a weird bump behind the teeth and it is very uncomfortable, hurts when i chew and food touches the spot. is this normal? how do i fix it?

That may be the interproximal gingiva that has been repositioned by the tooth movement. The gingiva will remodel over time. Bring this to your orthodontist's attention.

Selectively smoothing away part of the outer layer of dental enamel is a commonly used technique to make a little room for the teeth to move and be realigned. Sometimes the gum may be irritated by the process. If it has not resolved in a couple of days call your dentist back and let him know.