I say leave it be. Likely no one will notice but you.
Alternatively, you can spot clean it without much problem. Wet a paper towel, then dab the stained area (try not to scrub as it tends to remove more indigo). If the stain remains, try putting a bit of liquid detergent on the paper towel and dab further.
A year and some change (2-3 months) with my RGT SKs. 1 wash.
I've realized that the SKs are too skinny to be ubiquitously versatile, so I'm looking to purchase a pair of slubby Stantons. Any thoughts? (Fit, sizing, hand... Etc.)