Itching after cancer?

Hi all. So I have had colon cancer was fortunate it hadn't spread and was removed via resection 5 weeks ago. No further treatment needed just regular check ups. Recovery has been generally good but this last week my skin,  has become stupidly itchy (worse at night) and I get raised welts where I scratch ( no long nails here) I don't know if I should phone my specialist nurse (feel like now I am 'ok' maybe I shouldn't bother them) or just go along to my gp. Any ideas folks of what or why?