might have a chiro check him (any horse that has pulled back and broken loose should be checked over). I was at a horse show where a kid's show pony pulled back and broke out of the halter and flipped over. The pony was body sore, show vet checked it and said the pony probably just had muscle soreness from the recoil when the rope broke. vet advised to give the pony some time off, so after pasture rest they started riding and jumping the pony again. Pony was still sore and upon x-rays they found broken withers, poor pony! All that time and nobody bothered to check.

The short answer is don't tie him hard, either plan ahead and just lead him along or get one of those blocker tie ring thingies. The convenience of tying isn't worth the horse getting hurt or causing another horse to pull back and get hurt. Sure you could re-teach him to keep a float (slack) in the rope if you want, change his current expectation about tying.

"It's really quite amazing what a horse will do for you, if he only understands what you want. 
And it it's also quite amazing what a horse will do to you if he doesn't." ~ Bill Dorrance