My tomato plant has stated to have the leaves curling. Even the new leaves are a tight curl. I have noticed a lot of white looking small bugs(?). It concerns me about that. I was doing well before this infestation. It is in a container pot.
Probably what is happening is you have aphids a piercing insect. When aphids feed on a plant they cause cellular damage causing part of the plant to grow and tissue next to it be stunted causing curling. Without an image I cannot tell for sure. If the white little bugs don't move, then it is probably the molt of the aphid. Look to see if you see Green or Yellow Aphids on the plant. Good Luck