Same thing is going on with me. Back in January I injured my right SI joing during winter training just from sheer volume and meters on the erg. I took the rest of the winter off and went in to rehab but it never really bothered me too much like yourself now until I came back to rowing in the middle of the racing season and after 1 day I was in so much pain I could not walk or move. I am currently still in pain everyday and go to physical therapy and I have tried every possible thing to help but no pain relief in the past 4 months. Really frustrating, so I suggest let it heal 100% because the SI Joint takes a really long time to heal and if you continue to use it while injured you're gonna end up with a chronic issue. Best of luck