My 7 month old thinks his cot is made of rubber...

[Zachmeister]

...he is constantly pulling himself up on the cot rails but hasn't yet mastered the art of getting back down...tonight he banged his head quite badly...is there anything I can do apart from sit it out until he learns??

no

mine does this too - if he's not throwing himself against the rails he's eating them.

A paediatrician told me recently that they are unlikely to harm themelves by banging their heads on the cot. Not much comfort I know but not much else you can do I'm afraid