I recently got some lighter highlights in my hair that I'm not happy with. They came out chunky instead of small and spread out like I prefer. I want to ditch them and a friend said I could use a non permanent darker dye over them for now without hurting my hair too bad. Is this true?

Yes, you can use a semi-permanent hair color to cover the highlights. Semi-permanent color is formulated to last through several shampoos, depending on the hair's porosity. If you want the color to last, use a permanent hair. Whatever hair color you use, do a deep conditioning treatment at least once a week to make your hair healthy.