I think gd~'s explanation is about right. Probably you simmered it down until it was a bit too thick - though that can admittedly be hard to tell when you've been simmering it. Because when the liquid is hot, it's runnier. It cools off and gets more viscous, even at room temperature. Then you put it into the fridge and it gets solid.
I had a similar problem this year. I just have one maple tree of the variety worth tapping. I was going to take a few gallons of sap and make a small amount of syrup. When I tapped, the early sap flowed, and I collected about a gallon without too much trouble. But since the weather was in flux, the slow-dripping sap flow actually stopped for a couple days.
So I had this first gallon dehydrating on the stove (I avoided actual boiling, and also didn't heat it over night). Being a slow process, you can't watch the contents of the pot every moment, and the first batch got away from me. It got too thick and darkened... got to a condition like some kind of thick glue! I discovered it because a whole area of our house started to smell like a candy factory. So I immediately added water and stirred it in. That sort of took the process back to an earlier stage.
The sap started to flow again and I added the new sap, one pail-full after another, to the big pot. In the end, I was able to stop the simmering process at a proper level of dehydration and then cool the syrup and bottle it, and put it in the fridge. It was a matter of judgment, since I didn't have any sugar-content detecting instrument to work with.
My guess would be that what you've made is fine to eat. If you can get that stuff out of the jar, you could put it in a pan, add some water, and very gently heat it until the lumpy stuff dissolves into the water. Stir it around. Then, continue to warm it until it's a uniform syrup, pour it into your jar(s), cool it slowly, and see if you've arrived at an acceptable consistency.
