The answer is "Nemi".

In Jain tradition, "Jin puja se Gopal raja bana" refers to the story of Lord Neminath (Nemi), the 22nd Tirthankara. It is believed that by performing Jin puja (worship of Jinas or Tirthankaras), devotionally, one can achieve high spiritual status or even kingship, as in the case of Gopal becoming Raja due to his devotion to Lord Nemi. The answer "Nemi" fits the 4-letter requirement as well.