Achilles pain / 1 month til NYC

Hello! I am training for nyc and started feeling some Achilles pain during my week runs after my 18 mile long run two weekends ago. I haven’t been running on it for the past week and using the elliptical instead (it’s 100% pain free on the elliptical). I have been consistently using an ice/hot plunge after the elliptical in the mornings and then alternating ice and heat again at night. I am not sure how long this is supposed to last for or when to try running again. I am assuming I won’t be able to hit a 20 mile run in 2 weeks and ok with skipping it as long as I can get to the start line healthy. Wondering if anyone has any recommendations on how to treat this and be ready for NYC. Thanks:)