RSJ Quandary

Around 12 years ago I had a new kitchen fitted and a small part of the wall removed. I think it supports the small landing (it was the old pantry). At the time I didn’t think much of it when the builder kept asking me if I was definitely moving, and at the time I was but then changed my mind.
During the last few years it has been let out but now we are in a position where we want to sell it and I am scaring myself witless that it was not done properly. I remember the plasterer at the time mentioning that they done something like use roof joists, and embarrassingly I was too naive /ill educated to question it. I do remember mentioning something to the builder and he said “are you joking, a friggin elephant could jump up and down on it” so I subsequently left it there.
It is a 1930’s semi and there are some cracks that have appeared in the plaster (not deep ones but definitely around the area). We did have a new boiler fitted and the guy seemed pretty rough with his hammer (oh and also some fitted wardrobes taken out, so that could have been responsible for some of the damage too).
Anyway, I have mentioned it to the estate agent and he said not to say/do anything, but how could I live with it on my conscience if anything went wrong? If something were to happen, would it have happened by now? What steps if any should I take? I’m driving myself a bit nuts.

Any advice appreciated, I feel a bit of an idiot about the whole thing.

Oh jeez grow some FFS! Stop panicking, fill and paint over any serious cracks and try and think of something serious to worry about when buying and selling! Worst that will happen is you have to buy a pointless indemnity insurance to keep the numpty buyers solicitor at bay. If it was gonna fall down it would have.

As above, but just tread very carefully when going upstairs.

....and, although it is hay-fever season, try not to sneeze.

ACHOO