Suit shoulder problem (pictures inside)

Hard to say whats going on there. If you pull the sleeve to make it conform with your shoulder does that ridge flatten out?

Is it possible that the problematic shoulder is pitched forward compared to the other one, i.e., if you stand sideways, does one should protrude further than the other?

(I mean your actual shoulders, not the suit's)

Shoulder alterations are usually not cheap. Either something is wrong with the way that jacket was made or one of your shoulders is shaped oddly.

Yeah i feel like the problem is a combination of how you are wearing the suit, your posture/shoulder and the sizing of the suit.

It is bad posture as well as the actual fit of the coat. There is not much that can be done here but what has already been previously mentioned.

I don't think the suit is too small, i wear pretty small/slim suits and that has never happened.

Hard to say exactly what is wrong from your picture. Partly the fit and another part is the quality of the make. Jacket looks fused. Collar/neck look too small. Jacket shoulder looks too sloped to fit properly. jacket shoulder is "twisting", need to square and shift the shoulder. Not sure it is worth fixing as major surgery is required from a skilled tailor.

Despos has it right. This is likely the result of a poor quality coat. It is very likely fused. The collar does look slightly too small, but not enough to cause that sort of problem IMO. Any alteration from here would not be worth it as shoulder work will cost you, unless simply dropping the collar may help.

That all said, I gotta think a crease like that must be involving some sloping shoulder issue you may have.