Concern's rhymes with:
concerns, concerns', concerns, concerns', concerns, concerns', concerns, concerns', discerns, adjourns, berns, burnes, burns, burns', byrne's, byrnes, churns, concerns, concerns', discerns, earns, ferns, hearns, kearns, kern's, kernes, kerns, learns, mearns, querns, returns, returns', sauternes, spurns, stearns, stern's, sterns, ternes, terns, turns, vernes, yearns
Concern's sounds like:
censoring, coinsurance, concerning, concerns, concerns', concurrence, concurring, congruence, conjuring, conquering