Talk to Pediatrician on Vomiting And Motions

Aoa i'm from Karachi but currently in Multan due to Karachi weather. My question is for my son, hum 4 days pehly Multan aaye hain. he was fine but from last night mera beta vomiting ker raha hy kal raat b 2 ki or phr subha 1. Mainy ussy entrgermina 2b ka aik empule dia tha aj subha uss k baad ussy vomit ni aai but 3-4 motions kiay hyn uss ne din mai. Khana mai rice, daal roti, or milk b piya hy din mai to theek hi raha vomit ni hoi. But abhi raat ko feeder pi kr soya to half hour baad again vomit b ki or motion bhi.... I'm worried aisa kio ho raha? Maybe it is because of water change? Plz guide what should I do? He is taking Nido 1+ or ussy mild temperature b hy. evening mai check kia tha 100 tha