I suspect you used the lever in the Open position as a handle for tightening. Don't do that. And there may be rust involved.
- Start by putting a small bit of penetrating oil on the threads. Keep it off the rotor and brakes. Wait a bit.
- Use the lever in the open position (as pictured) and turn it anticlockwise.
If that doesn't help you might need a length of pipe or similar to act as a cheater-bar. You can also apply gentle heat using a hot air blower (not a burner!) to help the penetrating oil move. The threads are on the nut side only, but lubricating the lever side might help too.
- Once it does undo, clean the threads and inspect for damage and straightness.
If you find damage to the skewer, replace it. If you just can't turn it, then your last resort is to cut it off through the QR, just outboard of the dropout on the lever side. You won't damage the frame if you're careful, but you will need to buy a replacement QR front skewer.
When you do refit the wheel, the lever should be "hard" to swing into its final closed position but not impossible with one hand while using the other hand to hold the bike.
If you find this difficult to master, it may be worth returning to a solid axle with nuts.
Check your wheel rim for sideways play - I wonder if a cone nut has backed itself out, increasing pressure on the QR.
You might try slipping a cone spanner onto the cone nut where visible, and fractionally tightening it to relieve outward pressure. This will require a special cone nut spanner, and you'll need to reset the bearings once the wheel is out.