how to fill the contour in image

I have a tumour image, Ive extracted tumour from that and ive drawn a boundary across it. but the tumour portion is getting as a disc shape, I want to fill the black space inside the tumour with white and then draw the boundary. code and images are attached.

Answer 1

[KSSV]

Read about patch and fill

[rohith bharadwaj]

can you help with code. Im not getting how to use that

[rohith bharadwaj]

i dont want to create patch, i want to fill white in the patch extracted.