According to Pro Footballk Talk, Gronkowski also suffered a concussion on the play:
Gronkowski didn’t look overly woozy after the hit, rather displaying himself to be in an immense amount of pain understandably, so initial reaction wasn’t to suggest much other than the injuries we saw Gronkowski reacting to. However, watching the slow motion replay of the hit, it was clear Gronkowski’s head hit the Gillette Stadium turf quite hard before snapping back.
If there is any good news, it’s that the concussion was considered to be ‘slight’ but any injury to the head is worth noting, ‘slight’ or not.
It’s been reported Gronkowski could miss one year.