Entitlement to Delay Compensation

I had booked a flat for purchase in March, 2015. Agreement to sale had clause of handover within 30.6.2017(including 12 months' grace period), beyond which, the builder would pay a delay penalty as per the above agreement. When they were ready to handover, they mentioned via mail that I would not be able to take possession until registration of the property was carried out. I had already flagged the issue via mail that I was entitled to a penalty amount. But due to our immediate requirement to take possession, we had carried out the registration on 28.04.2018(as per joint decision) and had taken possession on 29.04.2018. However, during the registration process on 28.04.2018, they had got me to sign a paper, wherein, out of several other declarations, it was mentioned that I do not have any dues with the builder as per agreement to sale and any such due has been settled before registration. Given the circumstances on the day of registration, I was not in a condition to verify the contents of the letter. The penalty roughly amounts to Rs. 5 Lac. Is there a possibility that I can get my due via Consumer Forum?