Def mention to daycare about this conversation.
At this age I'd caution against 'feeding' words and ask for the information rather than prompt specifics (like 'boy') - you'll never know just how much is really your question being faithfully answered or an answer given to go along with the theme you're providing, so you may as well accept that you're going to have to put pieces together from what SHE gives you.
Like LZ said, my DS has become VERY creative and has a hell of an imagination lately, so I let him tell me the stories and pick out what rings true and reserve judgment for so much!
Also, at Matryoshka says, if there IS abuse going on it could be ANYONE with unsupervised contact. You're gonna have to go with your gut Kids are vulnerable because their bodies say the touching feels good but the context (i.e. the perpetrator) provides great discrepancy on top of threats for breaking the silence. Survivors of abuse feel party to the abuse because the sensations were not all unpleasant, and they feel they 'should have' hated every aspect of it. Complicated, especially in littlies.
Thinking of you and your DD