Should I get a revision rhinoplasty using rib graft? Will it make my nose bigger? I have very thick skin

A rib graft that is properly shaped will not necessarily make your nose larger although that it is a risk, unless it is signifincantly trimmed, and cartilage and or bone are removed to make room for the graft. I agree that the bridge could be elevated, but cartilage grafts whether from the rib, septum or ear all have associated risks of shifting positions or having an edge become visible.  They would not necessarily help the loss of definition of the tip which is due to scar tissue underneath the skin. without an in person consultation it is difficult to make firm recommendations, but I would probably recommend revision with removal of the scar tissue, and the use of cartilage grafts as necessary for support, but I doubt that rib would be necessary.  Close followup with steroid injections as necessary can often improve the tip definition, but not always. 

I would have your surgeon perform computer imaging of your nose to make sure you are on the same page as far as the result you would like to achieve from surgery. A rib graft will undoubtedly make your nose appear larger.

 There are many alternatives to augmenting the nasal bridge, and they include nasal septal cartilage, rib cartilage, ear cartilage, and synthetic implants. Each one has  their own advantages and disadvantages, which is best discussed at the time of examination and consultation. Revision rhinoplasty is one of the hardest operations to perform correctly  in the entire field of cosmetic surgery, so choose your surgeon very wisely based on experience