Areas around the doors are usually reinforced to some degree
to allow for some impact damage.
It's not unknown for airstairs or catering vehicles to cause such
damage to the aircraft structure, but thankfully these are very
rare events, and most equipment operators are very aware of
the consequences of their actions.
In my entire time in the industry I can only recall a few occasions
when an aircraft has had to be withdrawn from service as a result
of this sort of thing happening. Mainly because I was quite often
the bloke that had to repair the damage, and had a habit of venting
my spleen on whoever caused it.