I have a 1998 Nissan D21 4 cylinder truck

I have a 1998 Nissan D21 4 cylinder truck. The passenger side low beam stage of the headlight is out. Normally, I would just replace the bulb. However, the passenger side indicator light comes on on the passenger side when I turn on the headlights. The driver side indicator light does not come on when I turn the headlights on, put only the passenger one. The drivers side headlight works fine. I am just trying to figure out if this is a electrical problem that needs to be checked further or if I should just go ahead and replace the passenger side headlight bulb. Why are both indicator lights coming on or should they both be off? I also have a check engine light on the dash that will not go off and my mechanic says there is no reason for it to be on. I don't know if this is related or not. I just don't want to put money out for something that is not the problem. Thanks!