At the very least it’s an ear infection but it could be more serious. It could be a rupture. Have it checked by a doctor and if it’s nothing serious you may want to add regular use of swimmers brew to your after dive regiment. Swimmers brew is equal parts distilled water, 90% rubbing alcohol and white vinegar. Leave a few drops in your ears a few minutes with a cotton ball and clean with Q-tips. The alcohol will dry your ears and the vinegar will leave a slightly acidic environment that bacteria can’t grow in.