What is wrong with my dog?

my dog has a lump on his right side, by his shoulder its not hard its soft and there is nothing on the surface. last night he had trouble breathing it was like he was having a panic attack it lasted for about a minute and he was fine when i sat and stroked him and calmed him down then it happened again about 30 minutes later but he was fine soon after again. could they be linked? or what could either be?