Most likely. Only those two leaves? Remove affected leaves and dispose of out of the garden and begin regular spraying with fungicide of choice.

Dave

I see only two leaves and each one has just one lesion. I can't see the internal structure of the one on the right, but the one on the left looks like the beginning, possibly, of Septoria Leaf Spot to me, a very common fungal foliage disease,

Because of the way it's spread, via wind and embedded in rain drops, no doubt it would have affected ALL your tomato plants unless you bought just the one being shown and it was infected where you bought it or where whomever raised the seedlings that sold them to a nursery, farmer's market, etc.

Carolyn

To be on the safe side, I would spray with fungicide, as already suggested. Actually you should spray with fungicide on a schedule. I have done it couple of rounds already myself.
Prevention is easier than fighting disease.