My baby is crying heavily until he burps

My baby almost 2 years old is very picky and refuses to eat lots of time. He wakes up crying at night with his stomach feeling solid and cries out a lot until he burps and then only slowly his sobs will die down and he goes back to sleep. It started happening around the time he stopped feeding on milk and started on solids only around 13-15 months of age. It is infrequent but of late he had been crying almost every night, today even in the afternoon he had started crying. He was inconsolable and seemed like breaking into cold sweat. The stomach was a bit firm only when he had let the gas out his crying started to die down but slowly. After that his stomach seemed softer. What can I do in this situation.