Although we generally think of the two sides of our body as being exactly the same, this is not totally the case. If we look closely at the various parts of our body, it is common to notice small variations from side to side. For example, in women it is common for one breast to be larger than the other, and in men it is common for the testicles not be exactly the same. Similarly, it is generally totally normal for the ribs to appear slightly differently on one side than the other, and this is not generally a sign that something has gone wrong. Most of the time, differences in the ribs become more noticeable when people lose a bit of weight, allowing the ribs to stick out a bit more.
All that being said, issues like these may or may not be concerning, depending on whether you have pain, swelling, or another more serious symptom. I recommend that you mention this to your primary care doctor
; he or she can take a look and make sure everything is all right. In fact, these sorts of general questions are one of the main reasons to make sure that you go to your yearly physical check up!