First of all, if you are thinking of a career as a professional pilot, it is a good idea to go and do a Class 1 Aviation Medical at an approved aviation medical examiner's surgery (=doctor, = flight surgeon).
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I had a number of minor concerns when I started out - oh, so long ago! - and spending a few dollars for an appropriately trained doctor to tell me (a) if I was physically up to the standard and (b) what areas may become problems in the future, was money well spent.
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Like CosmicFrog I dwelled on some minor issues that grew into hurdles in my own mind. The doc basically said no major problems.
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Otic issues: I am susceptible to colds and hayfever. Always have been. Despite warnings, I made one or two attempts to fly unpressurised twins and 'get the job done' for my boss despite a headcold or difficult to equalise ears. *Learned pretty fast to just cancel the flight in future. *Painful, distracting and dangerous for my health and for my passengers.
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My employment contract allows me to take up to 6 days Upper Respiratory Tract Infection days per annum, in addition to cumulative sick leave. *If I get a cold and feel a blockage coming on, I ring in sick and claim the URTI day. *No loss of pay, and the company calls in the reserve pilot. Despite a susceptibility to ear blockages and head colds, I have never had to use all 6 days in any year.
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You probably are noticing the crackling in your ears only because you desire to be a pilot. Go get them checked out. My ears are crackling now as I type, come to think of it. *Crackling is not a problem, trapped gases are a problem. If you equalise by Valsalva or swallowing atction, not a problem.
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*Tricks of the trade...
Headcold or cannot equalise ears? Ring and advise unfit for duty.
Flying and ears feeling stuffy or likely to block? Attempt to equalise using Valsalva frequently. Very frequently. *Drink lots and lots of fluids to rehydrate. Avoid coffee and tea - try hot water flavoured with lemon. Tell other crewmembers. Plan long slow descents.
Also be alert to errors in depth perception and judging speed. Seem to remember a 727 accident in central america in the 1970's where a contributing factor in a runway overrun was the handling pilot had a head cold and flared high.
Good luck with your career.