We all do that at least a few times, and lots of us are STILL sowing too densely. (Most of us?)
If you have enough seeds left, starting over might be the most satisfying path. You clearly have a high germination rate and they look very happy except for being too crowded already. Maybe start a few more seeds right now while you wait for them to get big enough for surgery!
If you have another crop "coming on", you'll feel better about yanking, chopping and pulling the current crop of seedlings. BTW - what a great way to learn how to untangle seedlings! This might make you an expert, and lead to your own unique method of starting seeds. There is someone else on ATP who sows densely, deliberately, and then just rips them apart and uses the survivors. (Shudder!)
If you pop one of those clumps out and tease it apart on a plate, you should get least SOME viable seedlings from each clump. Remember you can cut away and kill several seedlings for each one you rescue, if they are too tangled.
Plant them when you get them untangled, but only one (or two) per cell or per pot. The reason to plant two per cell is if you expect half of them die. If most of them live, you still have to cut half off at the soil line.
While waiting to see if the brutalized seedlings survive, start a few more with just 1-3 seeds per cell, and separate those seeds as widely as possible within the cell.
Yes, it is very hard or almost impossible to get JUST ONE tiny seed in a pot or cell! Or even three.
There's a few things you can try, but I sure never mastered it with tiny seeds.
Pour the smallest number of seeds you can onto a saucer of contrasting color.
- - Maybe cut a soda straw diagonally and then cut it to a fine point.
- - Use the fine point to pick up a FEW seeds to drop on the saucer.
You'll still get too many seeds, so spread them around until there's an area with few seeds.
Use the point of a pencil or toothpick.
Moisten it.
Use it to pick up just ONE seed (or if you get 2-3, oh well).
Touch the pencil tip to the pre-moistened soilless mix in a small pot, cup or cell.
The moisture in the mix will grab the seeds.
If there were more than one seed, try to drag some of them away from the others.
After they germinate, cut all but one off at the soil line.
P.S. Tiny seeds need a fine surface on the mix, if they need to be sown "on the surface".
If you find a way to sow seeds THINLY (widely separated) , you can sow them in a "flat" - any old cup or shallow pot that's 3-12 inches in size. Let them all germinate and hope they ARE all separated by 1/2" to an inch.
When they have 1-2 pairs of true leaves, they will probably tolerate your "pricking them out" of the flat.
Treat them like harvesting potato plants: push a fork into the mix a little ways away from the seedling, so you avoid the roots.
Lever up a clod of mix including the seedling.
Transfer the whole clod to another pot.
Repeat for the other seedlings.
Or dump the whole "flat" and pick seedlings out of the mess. But that's tougher on the roots, I think.
Or use a fork to remove each clump of seedlings, drop the clump on a plate, and tease the clump apart.
I think it started being called a "flat" because people made them out of scrap wood, like 12" x 24" x 2-3". Overall, it was pretty "flat" compared to a pot.