Hi nayan, I also feel that a 5cm lump cannot have materialized in a very short and it must have been there for some time and has become noticable now. You should not neglect this swelling and even though your thyroid function tests
may be normal you should still go ahead and get a FNAC done to rule out any serious cause. FNAC is avery minor procedure and will not hurt you much more then a needle prick but it will be able to give lots of information especially whether the condition is benign or malignant that is whether it is cancer or noncancer. Usually papillary carcinoma
of thyroid is most common in men in your age group and it presents very insignificantly or without any symptoms. Once you have ruled out the growth to be non cancer then the choice is yours whether you want to be operated or not. Do not neglect your condition and take action now. Take care.