Should I be concerned that my little boy likes to play with dolls?

No. I encourage families to allow their children to explore all types of toys and to avoid labeling them as 'boy toys' or 'girl toys'. Playing with dolls allows boys to express and develop the nuturing skills they'll use as fathers. There is no reason to be concerned.
No. Little boys can play with dolls and little girls can play with cars! its all good creative playtime. The most important thing is to help them develop their imagination and creativity and give them opportunities for lots of playtime. Gender preference has not been shown to be affected by play toys.