There's a lump/swelling in the skin where my dog previously had a tick. Is that normal?

It is not uncommon for dogs to develop a little swelling in their skin at the site of a recent tick bite. It can take a while for these swellings to go down. The best thing to do is to keep the affected area clean and ensure your dog can not lick or scratch it (by for example using a buster collar). However, if your dog seems unwell contact a veterinarian.

If you live in a tick infested area it is wise to use tick prevention.