Working out issues ..

So I stayed afterschool to work out with this guy cause he has a group that work on something everyother day and so on. The first night I worked out. We did some weird push up thingy and then actual push ups which I loved and then calf rises and I got my split down. ( cheerleader) anyway, the next day I woke up and I felt my ribs were sore and one felt like it was popping out on the right side. If anyone knows why.. Please comment below. Today is day two and my mother has said nothing but muscle pains. Please and thank you!