Ear congestion - Blocked eustachian tubes. A bad head cold turned into a bad sinus and ear infection. Then, my ears got so congested it was hard to hear. I tried a variety of things. Finally, I went to the ear doctor, and she suggested an "ear popper". It is a small, handheld device which gently blows air into your nose. I guess it equalizes pressure inside and outside the eardrum or some such. After a day, my ears were clear most of the time. After a few more, the congestion was gone entirely. What a relief! You will probably need a doctor's prescription to order one, and they are expensive (about $175). So, like me, you might want to try other remedies first. But, if nothing works, then you might consider the "ear popper".
If she suggested a decongestant, I'd look for a product that says "decongestant" on the label. If it's an inner-ear infection or something like "swimmer's ear," there's no guarantee a decongestant will help, but it probably won't hurt to try it. If it keeps on for a few days, you might see your doc.