Hi Pradeepa,
This sounds like hormonal behavior and he is trying to nest, even without a mate. I would recommend finding a smaller food dish that he can’t sit in. For now, move the dish from where it is if possible. Be careful because he may charge you and try to bite you in order to protect his “nest”. In order to avoid this behavior, don’t let him have anything he can sit in like a large food bowl or a bird tent. You can also try moving his cage and rearranging his toys. Generally this type of behavior passes more quickly in male cockatiels.
Thank you for asking Lafeber,
Brenda