Headlights are for the front end of vehicles and NOT a woman's chest
Breast are more than a just a part of the female form. They probably should be considered accoutrements for fashion. Whether your preference is for revealing cleavage or a more conservative look, it's never good fashion etiquette to have your nipples poking through your shirt. You might need to put a band aid on this situation. Seriously. While padded bras will prevent your nipples from poking through, you may not like (or need) all the extra padding. Band aids may be the perfect way to use fashion finesse for this wardrobe malfunction. The large circular ones can usually provide enough coverage. I think this solution is great for the 'No Bra' days.