I have a slight swelling at the base of a 2 year old crown and root canal...no discharge or pain. not red or white bump just larger than other gums .

Depends: depends, if it it is just at the base of the crown you might just have a localized case of gingivitis in that area due to food trapping, lack of brushing well etc. I would just monitor the area as I continue to brush normal (with a little more attention given to that area) & if it get worse (where ibuprofen does not help pain) I would see my local dentist. No worries

Many possibilities: Possibilities include, but not limited to, failed root canal, fractured tooth, recurrent decay, food impaction, gum abscess, traumatic incident, burn, etc. please see your Dentist for differential diagnosis and appropriate treatment plan. Don't try to self-diagnose and self-treat. Get professional help.

Hard or soft?: If it is hard, it could be a benign bony exostosis. If soft, it could be a number of things either endodontic or periodontal in origin. Either way your local dentist needs to see it and evaluate it... can't be done over the internet.