I think I sprained my boob

I think I sprained my boob

Yesterday I reached into the back seat from the front seat in my van and strained to grab something because I was to lazy to get out of the car and open the door and get it, and I think I sprained my boob...or at least the muscle behind it. When I reach for stuff today or move a certain way or press on that area or when my kids sit on my lap on that side and lean back it feels like fire!!!!! Wahhhhhhh! It started hurting immediately after I did it but it's worse today ?