According to Dianna Marie Russini of ESPN who has been very accurate on her reporting of Rob Gronkowski over the years has said.
This injury could not have been too bad. If it was we would have at least seen him in a sling and it probably would have been following a surgery. I find this nothing to be worrying about but it does explain why he was not at OTA’s this summer.
On a good note you could not have told that anything was wrong with Gronk as he has been an animal at training camp lately. Gronk and Bennett have been lighting it up the past two weeks with Brady and Garoppolo as there QB.