I know you can stretch the neoprene neck seal on a dry suit if it's too tight.

Does anyone know if this can also be done on a wet suit?

What kind of collar you have?

If it's so tight that it's leaving your throat feeling bruised, it has to at some degree be affecting your carotids. That is just too risky to be diving with. You cpi;d have a gusset installed in the neck area to give you a tiny bit more room.

I would recommend that you contact either the manufacturer or their recommended service facility in your area to have it better fitted to you.

I presume that its neoprene.

My collar is not very tight, just uncomfortable. In the water I don't even feel it. I was just thinking if I can make it more comfortable outside the water.