I agree with PP - milk is far more important at this stage. Think of it as "food before one is just for fun"!
I wouldn't introduce any more solids until your LO is closer to six months old, and even then there's no hurry. It's mostly about exploring new textures and tastes at the start, rather than nutrition, so just follow his lead and try not to worry about how much he's eating
If you're worried that he's hungry, milk contains more calories per ounce than solids so at this age you're better off getting more milk into him than more solids, iyswim.
My LO started wasn't having solids three times a day until 7.5 months. We went to four milk feeds then, and three at around 11.5 months. The WHO recommends four milk feeds per day until one year.
HTH xx