Should I wait to upskill myself or contact professor about the PhD opening asap? I'm completing my Masters in Artificial intelligence. My thesis is about the social robotics and cognitive sciences. However, During my Masters, I've self-studied a little about big data and machine learning and I want to do my PhD in that area. Currently, I'll be done with my thesis writing in a week and after that I'll be working on machine learning and big data. 

Meanwhile, during my search of phd position, I have found one opening whose deadline is November'15. 

I have two options now:


I finish my thesis writing and get some machine learning concepts for around 1-2 months and then talk to the relevant supervisor.
I contact the professor now, showing my interest and keep in touch with him or ask him for guidance before joining the PhD with him?


I need your guidance in choosing the best option among two. In two months i think i'll have some basic concepts about the big data and data mining but i have to wait for two months and the position may not be available by that time. 

On the other hand, I have no prior work experience in the proposed Phd field, will the professor appreciate my interest and will help me to cover basics after finding me interested? 

Thanks.
I don't think you stand to gain much by waiting. Especially if, as you state in your question, the position might no longer be available within two months.

Either the supervisor is open to working with you and you'll have the opportunity to get to know him a bit and to demonstrate your ability to find your way in his field of research, or he's looking for a PhD student with a prior skillset you're unlikely to acquire in 1-2 months time anyway. 

If he's up for it, I'd say it's always a good idea to have a general talk with him to get to know your prospective field better, show your interest and to get targeted feedback on whether your Masters might simply be good enough in the first place. That doesn't exempt you from reading up a bit about his current research and it's background though.