"I am interested in chemistry."
Translation:Interesuję się chemią.
Googling the phrase shows 1280 results in total, first 2 pages are dictionary entries, on page 3 of results among some other dictionary entries you can find the first few actual uses, one of which is(taken from about me section of a blog):
Mam na imię Łukasz. Mieszkam na Litwie i uwielbiam gotowanie! Na dany moment mam 15 lat, ale gotuję i ciekawię się gotowaniem od 6 lat.
The other entries are forum o Wileńszczyźnie, another blog of Lithuanian person, a few Lithuanian pages (including Kurier Wileński)…
Based on that I would hazard a guess ciekawić się is regionalizm of Kresy dialect not spoken in Poland. ;)
While regional forms are not "wrong", it is a good idea to limit their use to regional communication, if for no other reason then to avoid miscommunication and perception of limited language skills(most people outside of given region will perceive regional forms as wrong, even when they are not).