This is a hard one. Essentially, your own chances if getting cancer are not affected by how much you worry about it - therefore don't worry about something that Might not happen.
Having said that, just be a bit vigilant. Don't suddenly get anxious about eg back pain at the first sign, because the chances are, it's just one of those things - you've had a virus and you're coughing ++ or you've been overdoing it on the heavy lifting front. Just give it a few days - is it getting better, or is it getting worse? If it isn't worsening, or it's getting better - probably nothing to worry about.
If it's getting worse, well it may be concerning, but not always. Definitely be seen if pain is getting worse, but it could still be an injury - they often get worse before they get better. Try ice, heat, simple pain relief. My point is that most pain isn't anything to be concerned about - it's concerning if it continues to get worse (over days to weeks, not just hours or days), it isn't relieved by simple pain killers (paracetamol and/or ibuprofen), it keeps you awake at night, you're losing weight, you lose your appetite, you're a lot more tired and lethargic than usual.
you can never be 100% sure, but the above things are what would be worrying