It is not only Hari Singh Nalwa but also Maharaja Ranjit Singh who never got due respect.
Afghans had ruled India except for the Mughal period. Mohmed Ghouri, Sher Shah Suri and Ibrahim Lodi conqured and ruled India. Babar had defeated Ibrahim Lodi, an Afghan in the first bettle of Panipat in 1526 to start Mughal dynasty. Later, Nadir Shah ( Iranian/Afghan) and Ahmed Shah Abdali defeated Mughals and in case Of Abdali also Marathas in the third battle of Panipat.
Traditional border between India and Afghanistan was Indus river. Maharaja Ranjit Singh consolidated Sikh Misls into a Sikh empire and spent 40 years ejecting Afghans out of Punjab. He pushed the border to the other side of Khyber Pass. Hari Singh Nalwa was the general who led the charge. Kashmir, Peshawar, Gilgit and many other areas of NW Punjab were all wrested away from Afghans. He sealed the Khyber Pass as the invasion route to India.
It was the English who enjoyed the fruits of Hari Singh’s and Ranjit Singh’s labor