From your description, you may have a unilateral leg swelling and I recommend you make an appointment with your primary care doctor
to be examined. Some of the causes of unilateral leg swelling that are of concern are deep vein thrombosis (DVT) and cellulitis. DVTs are blood clots that form in the veins which block the flow of blood which can lead to swelling or edema. DVT's are concerning because these clots can travel and migrate to the lung which can be life threatening because it prevents good oxygenation. The risk factors for developing a pulmonary embolus are smoking, obesity, immobility, and being female. You should consider stopping to smoke. Another possibility is cellulitis, which is infection of the skin. It can cause one sided swelling and cause redness in the surrounding area. It is usually warm to touch and demarcated. You should draw a line around it to see if it is spreading. You could potential have had a cut or abrasion in your field of work which cause have lead to cellulitis. Congestive heart failure can cause leg swelling but it is usually in both legs. Liver disease can also cause leg swelling but it is usually both legs. Again, you should make an appointment with your primary care doctor to make it checked out.