I have a problem on one of my tomatos, since I have only one sucessful tomato season under my belt, I do not know what the affliction is or what to do about it, but I do have a picture: 
I have a problem on one of my tomatos, since I have only one sucessful tomato season under my belt, I do not know what the affliction is or what to do about it, but I do have a picture:
That could be damage from a bug feeding on the tomato, like a stink bug?
Might need calcium.
Tomatoes are very sensitive to not getting enough calcium, which can be a problem if you gave acidic soil, that leaches the calcium away.
Sometimes wasps bite into a ripe tomato to cause that. There are two ways to fix that problem. One is Seven (7) dust,just sprinkle on veggies and leaves. Just be sure to wash them before eating. Second trick that I found was get them before the bugs do. Once they starting turning color, pull them off the vine and sit them in a window sill that gets some sun. Be careful though they, do ripen very quickly.Hope this helps
That spot looks like a bug has been dining on your tomato. Nothing to worry about unless he’s got a bunch of friends.
Most of my garden is shaded but that doesn’t really help in 100 degree weather. Tomatoes, corn, onions and beans are doing fine. Lettuce and greens have bolted. Gave up on the squashes and pulled them up so the garden is looking bare already. Maybe I’ll try again for fall.
Tip - don’t throw out the spring onion tops. Chop and freeze them. It’s so easy to throw in a handful when cooking.
Was given a bag of little cling peaches so there are now 6 quarts of chunks in the freezer. The pits and skins yielded 6 half pints of peach butter and 7 half pints of jelly. Hubby sampled the foam and says the butter tastes like Christmas, yum!
That looks like tomato anthracnose a soil-borne fungus disease, not severe in your pic, rainy areas are not good for it but good cultural practice such as not watering from above, not much help in rainy areas, and also mulching, looks like you have that covered. I had it once and it never got much beyond what you have and only on a few ‘maters. Still good eating though, just cut the bad part out.
Google or whatever it.