This year's World Mental Health Day theme is psychological first aid, I did nails in 2014 for this cause as well which you can find here. While a plaster isn't going to cut it for psychological first aid I think it is the general symbol for first aid.
Base Polish: Barry M - Lychee Glitter Polish: Models Own - Purple Haze Tights Polish: MUA - Frozen Yoghurt Stamping Polish: MoYou - Special Nail Polish - Black Stamping Plate: Bundle Monster H07