Hi Kathy,

You probably do not have much of a problem.  An issue arises because potatoes and tomatoes are both in the nightshade family.  Being in the same family results in them generally using and competing for the same nutrients in the soil, which may retard the growth of both.  This is a reason for treating them alike in a crop rotation, resting the soil to avoid depletion of the same nutrients year after year.  Similarly, the same family brings about susceptibility to the same diseases and insect pests, which is another reason for crop rotation in a bed.  A crop rotation cycle is recommended for gardens to promote growth and deter pests.  

In your case, the potatoes and tomatoes will not hurt each other directly.  However, if they are close together they will compete and may result in smaller crops, but the extent is hard to predict.  Both tend to sprawl, so it may be a problem.  I also suggest you follow fertilization instructions for your plants.

With our recent arrival of warm weather, I cannot imagine your tomatoes have been planted for long, so may still be able to transplant them to give them more space without competition.

Thank you for your question.