Image pixels value exceeds 0-255 range, after arithmetic operations on image - How to solve it

You could use mat2gray() to map the min to 0 and the max to 1.

I = mat2gray(I);

Multiply by 255 if you want in the range 0-255 and cast to uint8 if you want

I = uint8(255 * mat2gray(I));

I would recommend using a more descriptive variable name than I. You don't want it to be mistaken for a 1 or an l, and you don't want your code to look like alphabet soup.