prestige pressure cooker making a hissing noise from the side while cooking, is that normal?

First, check the pressure regulator weight. Make sure it's seated correctly on the vent pipe. If it's not, steam will escape from the side, not the top. Second, inspect the rubber sealing ring. If it's worn, cracked, or not seated properly in its groove, it won't seal. Replace it if needed. A steady hiss from the regulator is normal; a hiss from the lid seal is not.