A masonry chimney can be used to carry exhaust from multiple sources. These may include an open fireplace on this floor or a gas-fired boiler in the basement. Some chimneys have more than one flue (the duct inside the chimney that contains the fumes) and the flues can combine inside the masonry so that the number of flues that exit at the top may be fewer than the number of inputs.
Before you consider demolishing that brickwork do some work to understand what purpose it served. Look on the other side of this wall as well as below and above it to understand what it may be servicing. If you can inspect the top of the chimney you can confirm how many flues there are. There are at least as many purposes to this chimney.
If you are not familiar with masonry work I would suggest having a professional come in to give you an estimate on demolition. They can help you to figure out what the chimney is there for while giving you an estimate of what it costs to have it professionally removed.
Assuming you conclude that demo is a good idea it's a straightforward task for someone with the right skills. But keep in mind that the replacement brick and mortar will not perfectly match what is there now. You can remove the "hump" but you will still see where it was in the brick unless you follow up by painting or whitewashing the entire brick wall.