My daughter around age 4 became afriad of the dark, so we got a nightlight. My hubby wanted to fight me on putting the night light in because she was not afriad before but at this age kids minds are starting to develope at a new level which may create new fears for them.
When my daughter starts to ask for extra books, water and so on that I do not give into... bedtime is bedtime. Now I asked her WHY she did not want to go asleep or WHY she wanted mommy there she said she was afriad of the dark. I told her we can easily put a nightlight in her room. For a few days she still tried to push the boundries, which kids do so I stayed firm.
Now my daughter still has nightmares and I told her if she had a bad dream that first it is just a dream so not real and secondly she can call for mommy or daddy to get the comfort she needs after waking up from a bad dream (usually it is mommy who gets up). She has done this a handful of times in the past year so just the comfort of knowing that one of us will be there for her has helped. We also talk over any noises that she hears so she is not making up things in her mind while trying to figure out the sounds.
I would ask him if there is anything wrong or any reason he does not want to go to sleep. Do not put thoughts into his head by giving examples of bad dreams. If he says he is not sleepy simple tell him it is bed time and that you will be going to bed soon too. If he has certian fears try to address them BUT you need to know what they are you can not address fears if they are not there or made up.
My daughter is still not potty trained at night time/sleeping time so we make sure she uses the bathroom right befor bed AND we also let her know that she can get up to use the potty at night (she knows bed time is bed time and did not want to break rules by getting up to use the bathroom so would cry instead while wetting the bed). We also have a dry house so we told our daughter she can have a glass of water by her bed, and if it is empty she can get up once to refill it. Having rules and covering the bases as things change helps comfort a child as well as setting boundries for them.