i was upset and i didnt say anything. how do you process it 3 weeks later

ok so 3 weeks ago we had a meet n there was a moment where he did something w the other woman that bothered me. not like she did anything wrong, not like he did anything WRONG per se, but a thing i hadnt expected n that hit me weirdly. and i didnt say anything that night, didnt say anything at the debrief, n now its 3 weeks later n im still thinking about it. is it too late to bring it up? feels like its gonna come outta nowhere for him. but if i dont say it i think im gonna keep stewing. how do you raise something this far after the fact w/o it sounding like youve been hoarding grievances...