Yup don’t worry about it. Most sprinters have “compact muscles and light bone density” which results in the strange weight to size ratio.
I don’t think a low bone density would make you more injury-prone because most sprinters include plyometrics and you don’t really hear about them getting injured.
You’re not the only one, infact, I will list some sprinters for you:
Deji Aliu
Height: 187m
Weight: 75kg
Ato Boldon
Height: 176m
Weight: 75kg
Usain Bolt (When 17 years old)
Height: 196m
Weight: 75kg
Darrell Brown
Height: 184m
Weight: 70kg
Darren Campbell
Height: 182m
Weight: 72kg
Shawn Crawford
Height: 181m
Weight: 75kg
Maurice Greene
Height: 176m
Weight: 75kg
Darvis Patton
Height: 183m
Weight: 75kg
I think you get the point! 