Achilles pain

Hi! I’ve been training for the nyc marathon for the past 4 months and have gone injury free - last year I had a knee injury with a month left of marathon training and had to pull my entry - but starting three days ago my left Achilles is in constant pain. I’m in Sydney for a work trip the last week and didn’t realize how hilly it was, and I’ve been walking ~14 miles a day plus running so I think I’ve clearly been overdoing it. I’ve never had an Achilles injury before and am getting really nervous as I can barely walk without limping in pain. Any suggestions as to how I can quickly heal this or am I screwed?!?