Read online that reached full height does not equal to skeletal maturity ,does that mean my bone still can grow thicker?

Yes but . . .: We don't think in terms of "thickness" per se but rather density, more specifically bone density. So even if you've reached your maximum height due to closure of growth plates, you can get stronger bones. Our big concern is that bone strength or density will decrease later on as we age and increase risk of osteoporotic fracture. At 21yo, best for bones is eating healthy & exercising regularly

Just not taller: You reach your final height after the growth plates in your long bones close.After that point there is relatively minor changes in other sites.The thickness of your bones is determined by a complex interaction between your genetics,lifestyle (heavy labor/work),hormones &diet.You get thicker bones if your life involves manual labor/lifting/stress on the skeletan.