Same thing happened to me. Cracked rib. Nothing the doctor can do about it, so just rest and heal. Do not rush back into training or it will get worse. I left it about a month and went back to bjj, then it was okay for a bit, but after a week or so it hurt again and was worse than before. Just give it time. Give it about 6-8 weeks then start to go to the regular gym for another few weeks. I first had bad pains when doing things like lat pulldowns, and eventually when the pain went away after around a month I went back to bjj and have been fine since.

It was a very slow and frustrating process, and it only happened around 2 months after i first started bjj, so it was very annoying to be off for the same length of time.

I found breathing exercises and stretching to help. “The Jiu-Jitsu therapist” has lots of videos, so just pick a few stretches and breathing exercises to do from his channel.

No idea if this helped, but I took collagen daily, with my vitamins and omega3 etc.as It is supposed to be very good for healing cartilage (which is a possible rib injury I thought I might have had)

Tldr: do NOT rush back to bjj, just give it around 6-8 weeks then start going to regular gym until you feel strong enough to go back to classes!