First off, take your time, you have NOTHING To gain by being in a hurry.
ok relax, your not the first one who did this, nor will you be the last.
Get a good place to sit with a lot of good light.
examine the gun. any bumps ridges or other artifacts on the barrel showing perhaps a blocked bore or stuck bullet? no? good! yes? bad, empty the mag and ship to Remington.
oK back to looking, nothing showing that the gun has deformed in any way? good, remove the action and the barrel from the stock.
as you flip the action over, anything appear cracked or damaged from the bottom side?> no good. with the barrel down and over something like newspaper or towel. douse the openings of the loading/ejection port and the magazine cut out with Kroil, or similar pentrating oil, prop the gun in the corner and let it soak, repeat, repeat
if you have a vise, carefully clamp the action in the vice using a nice clean set of jaw pads or even a clean leather glove between the jaws and the action, again, take your time, going fast and making a huge gouge in the side of your action is not needed. I often wrap the action with masking tape and some leather for this.
With the action secured, and oil liberally dripping off the spots we wet down. try to wiggle the bolt handly in the appropriate range of motion.
douse with oil, try it again. If there is NO change in the feel or movement stop, if there is, add more oil, and using slow firm force, move that bolt back and forth a BIT more. I will often use a small block of wood between my palm and the bolt handle to save my hand. If the handle responds and moves, just keep doing until it feels like the bolt should function. sometimes a soft block of pine or a chunk of delrin or nylon can be used as a buffer between the bolt and the hammer/mallet. just tap it, hammering will break it loose. again hurrying now is a lost cause.
time and some effort will probable let it open