I still feel like I'm too young for these mystery injuries...

Woke up with an ache in my chest. It was exterior not interior, like where the pectoral muscle meets the bone. Definitely in the muscle. Now at the end of the day the ache has wrapped itself around to below my shoulder blade on the same side. I've not done anything strenuous today or yesterday. If I'm getting this already at 40 then 50 and 60 are gonna get rough 😓