1. You should have filed a complaint case before the local District Consumer Dispute redressal Forum alleging deficiency in service and unfair business practice praying for direction upon the builder to start construction immediately and pay damage and cost,
2. However, since you have already accepted the cheque towards refund of the said amount, send him a legal notice within 30 days of such dishonour claiming the amount with in 15 days,
3. if he fails, file an applicaton u/s138 of N.I. Act,
4. Engage a lawyer for the matter.