Since there's nothing you can do about it anyway, best to ride and observe. Use nail polish or touch up paint to fill the crack via the apply and wipe technique. Then you can quickly know if/when the crack begins to grow beyond where you've filled it.
BTW- there's no danger in riding it because it'll grow quite a bit before it breaks, and seatstay breaks are just about the least consequential.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.