2 years post BBL, I now have big hard solid balls in my both of my cheeks, what could be the cause and how can I get it fixed?

When performing a BBL, the fat graft should be injected in thin tubes to avoid the formation of lakes of fat, because the inner part will not survive, die and form a scar nodule. To confirm this hypothesis, a ultrasound scan or MRI should be made. If it is confirmed, direct excision is the preferred treatment. Best regards.

It sounds like you have fat necrosis and or scar tissue. Fat necrosis can be removed with liposuction or cut out. This may leave you with deformities in your buttocks, so a lot of BBL patients who develop this do not seek treatment unless they have pain from the fat necrosis. Aggressive massage can sometimes help to break up scar tissue.