People will often take “I felt like it” or “I thought it looked cool” for an answer. Halloween crossdressing is normal, though yeah some people will wonder if you’re questioning your gender, it’s more because it’s a common safe way to express that and any concern is likely from a desire to help.

And for what it’s worth I’ve known many cis men who like nail polish. Especially as an expression of goth, punk, or emo aesthetics where adopting feminine expressions are seen as cool for guys to do.