I had the exact same situation last year. After about a week of no improvement I went for an x-ray. Sure enough, cracks in two ribs. There is nothing you can do apart from let nature take its course. 3-6 weeks is said to be the normal recovery time; I was swimming gentle lengths after 2 weeks and back on the mat after 4.
My advice would be to get yourself x-rayed asap so you know what you're dealing with.
Thank you. Back on the mat in 4 weeks sounds a lot better than 8 weeks
My GP doctor did not think it was completely broken, but she did not advise me to have it x-rayed to be sure. Why is it important to know whether it is broken, cracked or bruised? (From what I read so far even with x-rays the diagnosis may be inaccurate and treatment and recovery seem very similar anyway.)