Painful bump beneath toes on ball. Appeared after standing a long time wearing heels. Will it go away?

At this point . It would be best to seek assessment by your podiatrist. The podiatrist can determine your condition, provide prognostic info and recommend healing measures. It is really important to wear shoes that make our feet happy.
Exam needed. Simple swelling of overused feet may resolve once you take it easy again... A fluid filled blister may take longer and may need to be drained of fluid, while a callus could indicate a need for special accommodations in your shoes to lessen the ground pressure.
Probally. Most likely swelling, wear flats to reduce pressure under the ball if your foot and the swelling should dissipate.