Not EXCERSISING for 3 weeks bad??? Seriously?

Well I I'm a teen boy skinny and I can't go excersise because of a small injury I usually play basketball every day but now can't so I haven't excersise for 2 weeks and sometimes I eat some junk food like coockies , bread , prosesed food but not everyday but I just don't want to get health problems from not EXCERSISING ???