Don't keep running the disposal when it is humming or motor will burn up.
You might need a plumber, and/or might need to replace disposal.
1) If the disposal cutter disc turns freely, and motor will not start then disposal has gone bad.
2) If disposal cutter disc is still stuck, then you might be able to salvage by removing two nuts on p-trap below sink.
P-trap drops free.
Remove 2 bolts holding tailpiece to side of disposal so you have access to plastic bag from below the cutter disc.
Keep removing plastic bag and keep working the wrench from below. It should eventually give way.
Put wood broomstick down sink opening and wedge broomstick against sink opening to get cutter disc to rotate.
Spray WD40 into opening to help lubricate the struck parts.
3) I wrote ez disposal replacement steps that also cover tips for reassembling p-trap.http://www1.fixya.com/support/r7929008-replace_garbage_disposal