Introduction of refined second-phase particles in superconducting YBa2Cu3O7-x (Y-123) matrix is known to be an effective route to improve the l-type pinning and the performance of Y-Ba-Cu-O (YBCO) single-grain superconductors, while the T-c-type pinning induced by spatial fluctuations in matrix composition is also important and contributes to the in-field J(c) performance and high-field applications of bulk superconductors. In this communication, chemical doping of nano-sized NiFe2O4 (mean size 50 nm) in single-grain YBCO superconductor is performed using a novel top-seeded infiltration growth (TSIG) technique based on a solid source pellet (SSP) of nano-Y2O3 + BaCuO2. The results indicate that, significant improvement of bulk performances including levitation force (33.93 N) and trapped field (0.3628 T) has been observed in the 0.2 wt% nano-NiFe2O4-doped sample, which are much higher than the undoped sample (28.81 N and 0.2754 T). T-c measurement indicates that, a decreased onset T-c of about 87.5 K and a broadened transition width of about 5 K are observed in the NiFe2O4-doped sample, indicating appearance of weak superconducting regions in superconducting matrix caused by Ni and Fe substitutions in Y-123 crystal lattice. This study supplies a practical approach to increase the YBCO bulk performance significantly.