The floor settling 2" in a span of, let's say 12', over a short period of time may be a major concern. Then again, in a two hundred year old house, with a larger span, maybe not.
You need to give us more to work with like:
How old is the house?
What type/style of house is it?
Is the basement finished or are the floor joist exposed?
Is the house one or two story?
Can you see signs of settling anywhere else in the house?
If you decide to jack the floor up, remember, as this floor goes up, so does whatever is above it and/or around it. Be prepared for some cracking of plaster, ceilings, and drywall seems.
Also, with the information that you have provided, this is a job that I would reccomend using a profesional for. Not that this is hard to use a jack but, if you use the jack in the wrong spot or improperly,or an under sized jack, you can do major damage depending on what is supporting the house.
If you could provide better information, we might be able to determine if you can do this project.