I'd guess either he is still hungry and wants more solids, or he is thirsty and wants some water or he wants some milk. When I started DS on solids he wanted milk after every solids meal for the first few weeks even though he had already had his milk feed an hour before.
I'd let him have as much solids as he wants unless you see his milk intake drop significantly (time at the breast and draining a breast or not, taking only one rather than two breasts etc). When he turns away from the food he is full or lost interest. I doubt you could over feed unless your were encouraging or forcing after he has shown signs of being full, which you aren't doing. (although I'm saying I doubt you can over feed there is a chance in some LOs will drop milk too quickly in pref for solids, if you noticed that then you could reduce solids a little or increase dairy solids as they do need their dairy/milk intake).
hth
