Burning plastic can release toxic fumes and chemicals that can be harmful if inhaled. In terms of the food you have already eaten, it is unlikely to be directly affected by the burning plastic handle on a frying pan unless there was direct contact between the food and the melted plastic.
However, if you were exposed to the fumes or the burning plastic produced smoke that came into contact with the food, there is a possibility that the food may have absorbed some of the harmful substances. In such cases, it would be advisable to exercise caution and monitor for any symptoms or signs of illness.
If you are concerned about potential health effects, it is always a good idea to consult with a healthcare professional who can provide personalized advice based on your specific situation. Additionally, it is important to ensure proper ventilation when cooking and to avoid overheating or burning plastic objects in the future to minimize potential risks.