Last step of nicotine extraction using DCM After using hydro-distillation method with distilled water and NaOH, separating the extract with dichloromethane, distillate it at 40 °C/104 °F, I'm left with some yellow pale oil.

I'm just wondering if traces of DCM could still be detected in the final product or if I need more steps to purify the extracted alkaloids ?
If you are worried only with DCM, then you should be fine since it is quite volatile. To be sure you have no DCM left in your nicotine leave it for a few days in a closed recipient filled with some dried silica gel or calcium chloride (here in my country those are easily found, even for domestic use), and if you are in a proper laboratory just leave it in the desiccator with the vacuum on for a few hours.

However, nicotine is hard to isolate since other alkaloids from tobacco are also extracted in the most commonly used methods. I don't know which extraction methodology you used but just for comparison, here are two papers with some information for isolating nicotine:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3263647/
https://www.ncbi.nlm.nih.gov/pubmed/19135499