So painful ?

Today I went for a swim (I don't usually swim for exercise and didn't before falling pregnant) but I couldn't run or walk so I decided to swim. I'm currently 9+5 weeks pregnant. I didn't even swim for 30 minutes and didn't strain myself but my arm muscles all the way to my breasts and my head are incredibly stiff. I can't even lift my arms above me head ??? I hope it heals quickly. Any remedies for stiff arms (by my arm pits through to my breasts) please!!