Should I buy the guy I'm seeing a 'funny' or a 'serious' present for Christmas?

I'm in my second year of university and have just come back home for Christmas. In uni, I've been seeing a guy for just over 7 weeks, we really like each other and are exclusive but we aren't boyfriend and girlfriend yet. Before I left to come home, we exchanged christmas presents.

We're both art students, and I had ordered him an art book focussing on an artist we both love. But it hadn't arrived in the post by the time I left, so I've told him I'll give him my present upon our return in January. His gift for me had arrived, however. He'd gotten me a Cheeky Bum Onesie ( http://www.asos.com/South-Beach/South-Beach-Madiso... ).

I think he didn't feel like he knew me well enough yet to buy me something that he knew I'd love so he just got me a silly present that we could laugh at. But I feel a bit self conscious of the present I've gotten him now. Should I buy him a funnier present before I go back to university, and pretend that I'd never bought him an art book? I don't want him to think I'd boring or serious or something..

What shall I do?