The question may be, do you actually need a license for your job--e.g. do you drive for work, such as to other locations, to clients or customers, to pick up stuff or deliver it. If you do, you clearly do need a license to do the job, and while it would be better had the employer actually checked before you received the job or that particular position requiring driving, they would have assumed that if you did drive, you had the license since you did not tell  them otherwise; they would then be within their rights to terminate you on discovering you did not have a license.On the other the other hand, you should not be fired for having been injured or on medical leave, at least  as long as there is a job you can do (a valid job) at that employer, including with some accomodations (e.g. a change in duties; some reasonably priced assistive technology). Therefore, if you think that you don't actually need to drive for the job and claiming you are being fired for that reason is just a pretext for firing you for some improper reason, such as your race, religion, sex, age over 40, or disability, or for taking some protected leave, then you should speak with an employment attorney.