S.N.
Hi J.,
It could definitely be because he is teething. I have talked with lactation consultants about this, and as long as he is still breastfeeding, he is getting all the nutrition he needs up until the age of at least one year old. The solid food you feed him at this age is really just for practice and doesn't get digested very well, so don't worry too much. Just keep offering him the solids and make sure he is nursing at least 5 times a day and he'll be back to eating solids in no time, I'm sure!