It is perfectly normal for 3 month old baby to vomit curd like milk immediately after feeding, especially while burping. This is more like regurgitation than vomiting, quantity is not so much. No need to worry as long as baby is gaining adequate weight and length every week as per standard growth parameters. Usually this problem settles down on its own once baby starts turning to prone position. Treatment with medicines is not always needed.
Next Steps
Keep doing regular burping after feeds. keep doing frequent monitoring of growth.