I have iching problem around my anus and its spreading.
How can I cure it?

A dermatologist (or regular MD) needs to look at it to determine what it is.
If it keeps spreading you really need a doctor!
Try this for now: Fill the bathtub with one inch of very hot water and add a gallon of vinegar and sit in it.
Try the same with Epsom salts.
Apply cortisone cream 1%.
Pat on witch hazel.
All the above are available at a grocery or drugstore.