Don't know if it's been posted since I've only skimmed some of the replies (fuck reading all 3 pages when time is short), but off the top of my head, I believe 20% HCl is used in the toilet bowl cleaner that I use, The Works, and the label on that is all scary like "Do not get into eyes or permanent blindness" and shit like that. I'm paraphrasing, but the warning label is all srs bsns. 20% HCl should be just shy of 6 mol/L.
For comparison, HCl concentration in gastric acid is about 5,000 ppm, or 0.5%, so that's quite a bit weaker than toilet cleaning fluid. So getting fresh vomit in the eye should cause irritation, but not blindness.
As usual, MC was probably thinking 3 steps ahead and isn't in actual danger from whatever it was that actually splashed on him.